When they finally write the history of this presidential election, the key names in the story could be those of Al Gore, George W Bush - and Theresa LePore.

Ms LePore is the superviser of elections for Florida's Palm Beach county. It is a place where the population mushroomed at the end of the 20th century, an affluent area which attracted tens of thousands of retirees from the north-eastern US, lured by the sun and the absence of income tax. A lot are Jewish, most are Democrats and, for many of them, their eyesight is not what it once was.

It was Ms LePore who decided that the ballot paper in Tuesday's presidential election in the county needed to be rearranged so elderly voters could read the names of candidates more easily. With 10 names to cram on the ballot, she decided that two pages would be better than one, and rearranged the ballot paper so that the two pages meshed with one another.

It was by far the biggest blunder of a series of Florida ballot irregularities and mysteries that have thrown the entire presidential election into chaos. It was a decision which led to 19,000 spoiled ballot papers being thrown into the bin on Tuesday night. And with them may have gone Al Gore's claim to the White House.

On the left-hand page of the ballot, Mr Bush's name appeared at the top, with Mr Gore's name below it. On the right-hand page, just between the two, was Pat Buchanan's name. This meant that although Mr Gore's name was second on the list, the hole which voters were required to punch to vote for him was the third from the top, below the holes for Mr Bush and Mr Buchanan.

Ms LePore showed her redesign to the two other people on the local canvassing board which supervises the county's elections, Carol Roberts and Judge Charles Burton. Both approved it for use on Tuesday. She showed it to representatives of the parties too. None objected.

Despair

It was a decision which may have decided the fate of US presidency, to say nothing of the health care prospects of millions of Americans, the right of women to have a legal abortion, the possibility of reform to the campaign finance jungle and the future of international nuclear weapons agreements, among others.

As a result of the confusion, thousands of voters in Palm Beach county did what they would not normally do. They voted for Pat Buchanan's rightwing, anti-Israeli, isolationist programme. When they realised their mistake, some punched a second hole on the ballot paper, invalidating their votes.

In Florida yesterday, the local newspapers and the airwaves were full of people in despair over what they had done.

"I would have voted for anyone but Buchanan," said Andre Fladell, a chiropractor from Delray Beach, who is one of several local voters preparing to take the issue to the courts. "When I left, I thought it was me, and I thought I had been careless. As I spoke to other people and I saw the ballot again, I realised I got suckered."

"I voted for Buchanan instead of Gore," said Siggy Flicker of Boca Raton. "I am Jewish and Lieberman is running, but I made the mistake. I was so humiliated and embarrassed and felt so stupid." Irma Fleischman from West Boca, who attended a rally on Wednesday where affidavits were being collected from people who say they voted incorrectly, added: "In a community like this, most people are very liberal Democrats. None of them would have ever voted for Buchanan."

In Palm Beach county, 3,407 people voted for Mr Buchanan, more than three times the number that voted for him in any other of Florida's 67 counties. Even Mr Buchanan thought yesterday that that was far more than he should have got. "I don't want votes that were not intended for me," he said.

But the really jaw-dropping figure was the number of ballot papers from Palm Beach that had to be discarded because they were punched twice. Ms LePore's office confirmed that 19,120 ballot papers were invalidated because of this error on Tuesday night. In the US Senate election in the county, only 3,783 people made a similar mistake.

Yesterday, Ms LePore was crestfallen and apologetic. "I'll never use facing pages like that again. I was trying to make the ballot more readable for our elderly voters. I was trying to do a good thing."

The complaints about Palm Beach county were at the centre of a series of planned legal challenges against the con duct of the election which could eventually lead to a fresh ballot in parts of the state, or even in the whole of Florida. Florida is no stranger to such lawsuits and reruns. The election for Miami's mayor had to be rerun as recently as 1998 after complaints of fraud. Large numbers of non-US voters - overwhelmingly Cubans - tried to take part in the original poll.

The argument about irregularities like those in Palm Beach county mounted as Florida continued to carry out a quite separate recount after Tuesday's election showed Mr Bush just 1,784 votes ahead of Mr Gore in an electorate of 6m.

Even when the recount is completed, the final result will not be officially declared until November 17, because overseas postal votes can still qualify until then, providing that they are postmarked on or before election day, November 7.

Most of the overseas postal votes are thought to come either from military voters stationed overseas, or from Florida residents currently in Israel.

Although Florida's elections division director, Clay Roberts, said yesterday that a ballot box that was apparently left behind in one Dade county precinct on election might - and widely shown on national television - contained no ballots but only election supplies such as marker pens, irregularities alleged to have taken place in Florida's poll include:

Intimidation of voters: In Woodville, outside Tallahassee, civil rights workers said that the Florida highway patrol set up a drivers' licence checkpoint near the local polling station, and charged that its purpose was to pressure black voters into staying away from the polls. A third of the local population in Woodville is black. A spokesman for the highway patrol denied the allegation and said that the officers handed out 13 tickets to white motorists and six to blacks.

A poll watcher for the National Association for the Advancement of Coloured People in Hillsborough County near Tampa said a police deputy posted out side a polling station asked black men for identification and turned them away after checking police records.

Address changes: One of the most widespread complaints was that voters who turned up with evidence of their changes of address were not allowed to vote because supervisors were unable to obtain authorisation from electoral authorities. This is normally a standard procedure for which telephone authorisation is regularly given, but lines were jammed across the state.

"I got through once, at 7.30 in the morning," said Nat Rothenburg, a poll supervisor in Lauderhill, where 500 voters were turned away. "I felt so bad for these people who wanted to vote." Hazel Bostwick added: "I had clerks pulling out their hair because they couldn't get through. It was not fair. It was not fair."

Closing of polling stations: People in several parts of Florida complained that they were unable to vote because polling stations were closed and no instructions were posted about alternative sites.

A school in Pompano Beach which had been advertised as a polling station remained closed all day. The turnout in that precinct was only two-thirds the turnout for the county as a whole. In Miramar City, constituents were directed to vote at a local fire station which was not in use as a polling station. In Hallandale Beach some voters said they were told the election "would be tomorrow" - Wednesday.

Inaccurate voter rolls: Officials received many complaints that individual voters were not allowed to take part in the election because their names were incorrectly omitted from the rolls. At Pembroke Pines, up to 50 apparently qualified voters were turned away because they were not registered. A similar complaint was reported in North Lauderdale. Billie Young, a voter in Tamarac, was told that she was not allowed to vote because she was registered as dead.